Telephone.



F. G. SARGENT.

TELEPHONE.

APPLIOATION FILED MAR. 3, 1909.

94:0,284:. Patented Nov. 16, 1909.

UNITED sr 'rEs rnTENT OFFICE.

FREDERICK G. SARGENT, OF WESTFORD, MASSACHUSETTS.

TELEPHONE.

Specification of Letters Patent.

Application filed March 3, 1909. Serial No 4s, 1eo.

To all whom it may concer':

Be it known that I, FREDERICK G. SAR- GHNT, a citizen of the United States, residing at VVestford, in the county of Middlesex and State of Massachusetts, have invented a new and useful Telephone, of which the following is a specification. v

This invention relates t'o telephones, particularly those adapted for wireless use. The power in this class of instruments can be increased up to a certain limit by increasing the number of turns orconvolutions of wire about the electro-magnet, but of course this increase is limited on account of the high internal resistance created by increasing the number of turns, and on account of various magnctic and .nechanical effects which, as is well-known, are produced in electro-magnets. Particularly in wireless telephony it has been found in practice that a telephone receiver should not have the maximum number of convolutions necessary to produce the greatest motion of the diaphragm armature, but that there is always a certain number ot convol-utions and therefore a certain resistance which gives the maximum efliciency, this number being determined of course, by the conditions present at any given time. Under the varying conditions in wireless telephony at the present time, a receiving instrument which has been constructed to give the greatest eificiency under the conditions normally prevailing is cometimes called upon to do duty under other conditions in which it does not have a maximum efliciency.

` The rincipal object of this invention is to provide a telephone instrument, particularly a receiver, in which the number of convolutions, and consequently the internal resistance, can be Vared at will, so that it can be used under varyin conditions with the maximum degree of e ciency in each case.

F urther objects and advantages of the invention will appear hereinafter.

Reference is to be had to the accompanying drawing in which- F igure 1 shows a longitudinal central sectional view of a telephone receiver Constructed according to this invention, and Fg. 2 is a diagrammatic view 'of the windngs.

This receiver is shown as comprising a casing 10 in which is mounted a magnet 11 of a Well known form, diaphragm 12, and other features of a receiver. One terminal of the electro-magnet is connected by a wire 13 in the casing with a terminal 14 into which a 'plug 150 can be inserted or fixed to constitute one conduct-or from the receiver. The electromagnet is wouud in a plurality of coils having several diterent terminals 15, 16, 17 'and 18. Each of these terminals is shown in the present instance as provided with a -socket into which a plug 20 can be inserted, constituting the other terminal ot thedevice( It will be understood that the Wire of which the electro-magnet is wound passes several times around the spool from the terminal 13, and then is brought out to one of the terminals for receivin` the plug 20, so that if the plug is introduced into the first terminal, the eXcitation of the magnet and its internal resistance will be of the minimum degree. The magnet is also provided with an additional winding pref: erably in series with the first winding and connected with the second terminal for receiving the plug 20, so that if the plug 20 and resistance can be increased by the use i of any number of additional terminals for the plug 20, four of which are shown in the present instance. It will be seen therefore that as the instrument will. ordinarily be constructed so that for its usual duty some one of the intermediate terminals will be best to use, under any extraordinaryconditions where it is found the instrument does not work very well, the operator from his experience can tell whether the plug 20 ought to be moved in such a way as to increase or decrease the resistance, or he can experiment with it until he finds a position for the plug which gives the best results under those conditions. e

While I have illustrated and described a preferred embodiment of the invention', I am aware that many modifications may be made therein by any person skilled in the' first named terminal its other terminal can 1 be connected with any one of said plurality of tenninals, and one 01' more of the coils on the electro-magnet wi11`be brought into the I crcuit in series.

2. In a telephone 'eceiver, the conbination of an electro-magnet having a plnrality of coils, a terminal connected with all of said coils, a plurality of terminals located along the shank of the recever, each connected with one of said coils, whereby when i a conductor having two terminals is con- 15 nected with the first n'amed terminal its othcnterminal can be connected with any one of said plurality of terninals, and one or more of the coils on the electro-magnet i will be brought into the circuit.

In testimony whereof I have hereunto set i my hand, in the presence of two subscrbing witnesses.

FREDERICK G. SARGENT.

'witnesses WILLLAM F. SARGENT, OSBORN H. CILLEY. 

